Spooling Electroluminescence Spectroscopy of Ru(bpy)₃²⁺ Light-Emitting Electrochemical Cells with an Atomic Layer Deposited Zinc Oxide Electron-Transporting/Hole-Blocking Interlayer

Light-emitting electrochemical cells (LECs) are being developed as an alternative to traditional OLEDs for lighting applications. In this study, a 10 nm conformal ZnO electron-transport/hole-blocking interlayer was applied via atomic layer deposition to Ru(bpy)32+ (RuBPY) model LECs, resulting in a 4-fold luminance enhancement from 7.1 to 28 cd/m2, along with a significant improvement in device sustainability and lifetimes. The device electroluminescent efficiency was increased by 175%. Spooling electroluminescence spectroscopy was used here for the first time, showcasing the in situ monitoring of LECs. ZnO-RuBPY-LECs showed extremely stable red-orange emission at 645 nm, while reference RuBPY-LECs demonstrated a 20 nm blue-shift, attributed to device degradation.